Applications and Challenges of Redox-Mediated Catalysis in Lithium-Air Batteries ★

The lithium-air battery has been attracted around the world owing to very high energy density, which could well satisfy the increased energy requirement from electronic devices, especially the electric vehicle.1-3 However, despite large R&D efforts devoted to its implementation, several issues have so far limited the performance of the lithium oxygen battery because of few discharge-charge cycles, large polarization and low rate capability.4, 5 Some researchers used many materials for cathode in lithium air batteries because inherent activation effect and morphology of each material had an effect to decrease polarization and increase capacity. Although carbon has been talked making by-product like Li2CO3, it is the mostly used material because of the advantage in the way that amount and cost. Some paper told that not only carbon but also electrolyte co-makes this side reaction problem in lithium oxygen battery system. In this study, a new physical pulverization strategy has been developed to prepare a highly active composite of CoOx and crushed graphite (CG) for the cathode in lithium–air batteries. The effect of CoOx loading on the charge potential in the oxygen evolution reaction was investigated in coin cell tests. The CoOx (38.9 wt%)/CG composite showed a low charge potential of 3.92 V with a delivered capacity of 2 mAh/cm2 under a current density of 0.2 mA/cm2. The charge potential was 4.10 and 4.15 V at a capacity of 5 and 10 mAh/cm2, respectively, with a current density of 0.5 mA/cm2. The stability of the electrolyte and discharge product on the gas-diffusion layer after the cycling were preliminarily characterized by 1H nuclear magnetic resonance spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The high activity of the composite was further analyzed by electrochemical impedance spectroscopy, cyclic voltammetry, and potential-step chronoamperometry. The results indicate that our near-dry milling method is an effective and green approach to preparing a nanocomposite cathode with high surface area and porosity, while using less solvent. Its relative simplicity compared with the traditional solution method could facilitate its widespread application in catalysis, energy storage, and materials science.

A new physical pulverization strategy has been developed to prepare a highly active composite of CoOx and crushed graphite (CG) for the cathode in lithium-oxygen batteries. The effect of CoOx loading on the charge potential in the oxygen evolution reaction (Li(2)O(2) →2 Li(+) +O(2) +2e(-)) was investigated in coin-cell tests. The CoOx (38.9 wt %)/CG composite showed a low charge potential of 3.92 V with a delivered capacity of 2 mAh cm(-2) under a current density of 0.2 mA cm(-2). The charge potential was 4.10 and 4.15 V at a capacity of 5 and 10 mAh cm(-2), respectively, with a current density of 0.5 mA cm(-2). The stability of the electrolyte and discharge product on the gas-diffusion layer after the cycling were preliminarily characterized by (1)H nuclear magnetic resonance spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The high activity of the composite was further analyzed by electrochemical impedance spectroscopy, cyclic voltammetry, and potential-step chronoamperometry. The results indicate that our near-dry milling method is an effective and green approach to preparing a nanocomposite cathode with high surface area and porosity, while using less solvent. Its relative simplicity compared with the traditional solution method could facilitate its widespread application in catalysis, energy storage, and materials science.

Materials science is an inherently interdisciplinary research field, which involves physics, chemistry, and biology. The research of materials science emphasizes understanding a material's structure, and thus its properties and performance, through multiple capabilities ranging from synthesis, processing, and characterization to theory. As materials are the basic substances that make up all everyday objects, materials science is so important to nearly every aspect of science and technology in human existence and social life.

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Disentangling plasmonic and catalytic effects in a practical plasmon-enhanced Lithium–Oxygen battery

Ameliorating round‐trip efficiency and mitigating parasitic reaction play a key role in enhancing the activity and durability of lithium–oxygen batteries. Herein, it is first reported that Ti3C2 MXene quantum dot clusters full of rich crystal defects anchored on N‐doped carbon nanosheets (Ti3C2 QDC/N‐C) can operate well as bifunctional catalyst for Li–O2 batteries. The well‐defined grain boundary and edge defects make crucial contributions in modulating the local unsaturated coordination state of active titanium atoms and thus the electronic structure of Ti3C2 QDC/N‐C, greatly enhancing the catalytic capability. Furthermore, density functional theory calculations disclose that the fruitful crystal defects governed catalytic centers endow substantial benefits for inducing charge density delocalization, regulating the LixOy intermediate adsorption and reducing the oxidation‐reduction energy barriers. The geometric morphology and distribution of final Li2O2 accommodations are distinctly altered with optimized decomposition reversibility, which strengthens electro‐catalytic kinetics and lowers redox voltage gaps. As expected, Li–O2 cells based on Ti3C2 QDC/N‐C show favorable long‐period stability (240 cycles at 200 mA g−1) with minimal side reactions and distinguished discharge/charge overpotential (0.62 V). Critically, this crystal defect strategy paves a new way for expanding the active sites in MXenes for catalytic applications.